Single carrier wireless telecommunications systems are known. In those known systems, radio coverage is provided to user equipment, for example, mobile telephones, by geographical area. A base station is located in each geographical area to provide the required radio coverage. User equipment in the area served by a base station receives information and data from the base station and transmits information and data to the base station. In a high speed downlink packet access (HSDPA) telecommunications network, data and information is sent between user equipment and a base station in data packets on a radio frequency carrier.
Information and data transmitted by the base station to the user equipment occurs on radio frequency carriers known as downlink carriers. Information and data transmitted by user equipment to the base station occurs on radio frequency carriers known as uplink carriers.
In known wireless telecommunication systems operating in single carrier mode, user equipment can move between geographical base station coverage areas. Service provided to user equipment is overseen by a radio network controller (RNC). The radio network controller communicates with user equipment and base stations and determines which base station each user equipment is primarily connected to. Furthermore, a radio network controller acts to control and communicate with a base station and user equipment when user equipment moves from the geographical area served by one base station to a geographical area served by another base station.
It has been proposed to allow base stations and user equipment to each transmit simultaneously on more than one carrier. Furthermore it has been proposed to allow user equipment and base stations to receive simultaneously on more than one carrier frequency. Each carrier, both uplink and downlink, is typically independently power controlled and independently scheduled by a base station. Provision of more than one downlink carrier, for example, on four frequency carriers, allows for an increase in data throughput to the user equipment. Networks having more than two carriers may be referred to as “multi cell high speed downlink packet access” (MC-HSDPA) networks. The term “multi-carrier” network used herein is envisaged to cover the case where two, three, four, or more downlink (or uplink) carriers are provided for in a network.
Provision of multi-carrier functionality may have associated problems. Accordingly, it is desired to improve the operation of a wireless telecommunications network having multi-carrier functionality.